"The government is now tightening the rules surrounding bestiality so there will be no doubt about the fact that it is prohibited to inflict suffering on animals," Minister for Rural Affairs Eskil Erlandsson said in a statement.
"There should be no doubt that bestiality is unacceptable."
Until now, bestiality was illegal in Sweden only if it could be proven that the animal had subjected to suffering.
From January 1, any sexual act with an animal will be punishable by a fine, a maximum prison sentence of two years, or both, even if the animal shows no sign of injury or suffering.
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"It's very important that society makes a clear statement that it is unacceptable to use animals that way," he said.
The ban will bring Sweden in line with a European Union directive.
Germany introduced a ban in December, following in the footsteps of Britain, France, and Switzerland among others.
The Swedish parliament is expected to pass the bill into law soon, as there is broad political consensus on the issue.
According to Beck-Friis, under the current law veterinarians may suspect that an animal has been sexually abused but they are generally unable to prove it.
In 2006, the latest year for which statistics are available, about 100 cases of animals suffering injuries suspected of being related to bestiality were brought to the authorities' attention, Beck-Friis said.